The present invention relates to an inspection stage on which an object to be inspected is mounted and an inspection apparatus provided with that inspection stage. More specifically, the present invention relates to an inspection stage that does not slant even when a chuck top on which the object is placed is exerted with an offset load during inspection.
Conventionally, a probe apparatus is employed as an inspection apparatus for inspecting an object such as a semiconductor wafer. The probe apparatus is provided with a loader chamber for conveying a wafer and pre-aligning it, and a prober chamber for receiving the wafer from the loader chamber and inspecting the electrical characteristics of the wafer. Inside the prober chamber, an inspection stage is provided. The inspection stage is adapted to hold a wafer mounted thereon, and is movable in the X, Y and Z directions. A probe card is arranged above the inspection stage. With the inspection stage moved, the object to be inspected is positioned with reference to the probe card. Then, the object and the probe card are electrically connected to each other. The probe card is connected to a measuring apparatus, by which the electric characteristics of the wafer are inspected.
An example of a conventional inspection stage is shown in FIG. 5. As shown in this Figure, the inspection stage comprises a chuck top 1 on which a wafer is mounted, a Z shaft 2 (e.g., a ball screw) extending downward from the center of the rear side of the chuck top 1, a Z shaft guide 3 for guiding the vertical movement of the Z shaft 2, and a vertical driving mechanism 4 for moving the chuck top 1 up or down along the Z shaft guide 3. The inspection stage is movable in the X and Y directions and positions the object with reference to the probe card. After the positioning, the chuck top 1 is moved up in the Z direction, thereby permitting the object W to come into contact with a probe card (not shown in FIG. 5).
In recent years, IC chips are integrated at higher density than before. Hence, an object to be examined has a large number of electrode pads, and these are arranged at very short pitches. The probe card has an increased number of contact terminals, accordingly. In addition, the number of objects that are measured at a time is also large. This being so, the load that the contact terminals apply to both objects and a main chuck when they are brought into contact with each other, has increased to a value which is between dozens of kg and 100 kg. When, as shown in FIG. 5, a peripheral portion of the object is inspected, the load P exerted to that peripheral portion is between dozens of kg and 100 kg, and the Z shaft guide 2 leans to one side, due to the insufficient rigidity of the Z shaft guide. As a result, the chuck top slants, with the Z shaft-driving mechanism 4 as a center of the slanting movement, as indicated by the broken lines in FIG. 5. If this occurs, the object and the probe card are not brought into uniform contact with each other. Since there are some contact terminals that fail to come into contact with the probe card, the reliability of the inspection is degraded.
Due to the above-noted load exerted during inspection, the Z shaft 2 may move through the Z shaft guide 3 in a slanted state. If this happens, the Z shaft guide 3 is damaged.
To prevent the chuck top from slanting, it may be thought to employ a long Z shaft guide 3 or to increase the number of balls. These measures, however, do not solve the problem stemming from the insufficient rigidity of the guide shaft 3.
As shown in FIG. 6, it is possible to employ a Z shaft 2A having a large diameter. As shown in FIG. 7, it is also possible to employ a plurality of Z shafts 2B. The former method is useful in improving the rigidity of the Z axis 2A, and the latter method is useful in reducing to the load applied to one Z shaft. Even if these measures are taken, however, the chuck top 1 is exerted with an offset load whose center lies in the vertical driving mechanism 4. This means that the above measures are insufficient to solve the slanting of the chuck top 1. In addition, the inspection stage and the inspection apparatus are inevitably large in size.
The present invention has been developed in consideration of the above problems.
Accordingly, an object of the present invention is to prevent a chuck top from being slanted even if the number of contact terminals provided for a probe card is large, and the number of objects to be examined at a time is large, accordingly. The present invention is therefore intended to provide an inspection stage and an inspection apparatus that ensures high inspection reliability.
According to one aspect of the present invention, there is provided an inspection stage comprising:
a main chuck on which an object to be examined is mounted;
a support table for supporting the main chuck;
a support table lift mechanism including a plurality of Z shafts for supporting the support table, and a Z shaft vertical drive mechanism for vertically driving the Z shafts;
an X stage on which the support table lift mechanism is mounted and which is movable in an X direction; and
a Y stage which supports the X stage and being movable in a Y direction.
In the inspection stage, it is preferable that the support table lift mechanism include a vertical position control device for controlling vertical positions of the Z shafts individually.
In the inspection stage, it is also preferable that the support table lift mechanism be located on an outer side of the main chuck.
In the inspection stage, it is further preferable that the vertical position control device include a slant detection mechanism 27 for detecting the degree of horizontality of the support table. On the basis of the degree of horizontality of the support table detected by the slant detection means, the vertical position control device controls the vertical positions of the Z shaft so as to keep the degree of horizontality of the support table within a predetermined range.
According to another aspect of the present invention, there is provided an inspection apparatus comprising:
a loader chamber in which a plurality of objects to be examined are received;
a prober chamber for inspecting the objects fed from the loader chamber; and
an inspection stage arranged inside the prober chamber,
the inspecting stage including:
a main chuck on which an object to be examined is mounted;
a support table for supporting the main chuck;
a support table lift mechanism including a plurality of Z shafts for supporting the support table, and a Z shaft vertical drive mechanism for vertically driving the Z shafts;
an X stage on which the support table lift mechanism is mounted and which is movable in an X direction; and
a Y stage which supports the X stage and being movable in a Y direction.
In the inspection stage, it is preferable that the support table lift mechanism include a vertical position control device for controlling vertical positions of the Z shafts individually.
In the inspection stage, it is further preferable that the vertical position control device include a slant detection mechanism 27 for detecting horizontality of the support table. On the basis of the degree of horizontality of the support table detected by the slant detection means, the vertical position control device controls the vertical positions of the Z shaft so as to keep the degree of horizontality of the support table within a predetermined range.
According to the third aspect of the present invention, there is provided an inspection stage comprising:
a main chuck on which an object to be examined is mounted;
a support table for supporting the main chuck;
a support table lift mechanism including three Z shafts for supporting the support table, a Z shaft vertical drive mechanism for vertically driving each of the Z shafts, and a vertical position control device for controlling the vertical position of each Z shaft, the vertical position control device having a linear sensor for detecting a position of the support table, and another linear sensor for detecting the degree of horizontality of the support table;
an X stage on which the support table lift mechanism is mounted and which is movable in an X direction; and
a Y stage which supports the X stage and being movable in a Y direction.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.